• Journal of Electrochemical Science and Technology
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• v.14 no.4
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• pp.333-348
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• 2023

In this study, a 3D model of the proton exchange membrane fuel cell is established, and a new 3D baffle structure is designed, which is combined with the parallel flow field and then optimized by numerical simulation methods. The number of baffles and the cross-sectional trapezoidal base angle are taken as the main variables, and their impacts on the performance indexes of the cathode side are analyzed. The results show that the 3D baffle can facilitate the convection and diffusion mass transfer of reactants, improve the uniformity of oxygen distribution, enhance the drainage capacity, and make the cell performance superior; however, too small angle will lead to excessive local convective mass flux, resulting in the decrease of the overall uniformity of oxygen distribution and lowering the cell performance. Among them, the optimal number of baffles and angle are 9 and 58°, respectively, which improves the net output power density by 10.8% than conventional flow field.

• Journal of the Korean association of regional geographers
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• v.3 no.2
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• pp.19-35
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• 1997

The purpose of this study is to find out the characteristics of landform in Geoje-Do using GIS and DTED data. The characteristics of landform in Geoje-Do are as follows; First, the height-range of Geoje-Do is $0{\sim}580m$, and the average elevation of it is 124m. Volcanic and granite region is mainly appeared at high elevation-region. But, we can't find out outstanding difference of elevation, according to its geology. The second. the slope-range of Geoje-Do is $0{\sim}52$ degree, and the average slope of it is 17.6 degree. The slope of volcanic and granite area is more steeper than any other region. But the results of analysis of the geology in Geojo-Do, don't show outstanding difference of the slope. The third, the area-rate of the aspect of Geoje-Do is almost same in all direction. And the area-rate of south-west direction is the highest. According to the geology of Geoje-Do, granite is distributed the most widely, and the area of volcanic and granite occupy 60% of entire island's area. According to analysis of influence of geology with elevation, geology has little relationship with elevation. According to analysis of geology and drainage network, streams are inclined to be developed well in Alluvium area. Drainage network is well developed throughout the entire island, except southeast area. The highest order of stream is 4 in 1:25,000 topographic map. The density of stream in Geoje-Do is very high, such as 1.6. The bifurcation-ratio of stream is also higher than 4 in all order. The length-ratio of stream is ranged from 1.24 to 3.25. According to the relationship between order and elevation. order is the greater, elevation is the lower. According to the relationship between order and slope, order is the greater, slope is the gentler. In this study, we use DTED Data, and compare it with topographic map data. According to the comparison, there is a little difference between DTED data and topographic map data. Therefore, to use DTED data in landform analysis, it is required coordinate matching process. This process is very important, and take very long time. Thus, if you use DTED in landform analysis, some processes are required. DTED data can be taken very easily, but its using is not simple. Because coordinate adjust is very hard work.

• Economic and Environmental Geology
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• v.37 no.5
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• pp.521-532
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• 2004

The aim of this study is to evaluate the susceptibility of landslides at Kangneung area, Korea, using a Geographic Information System (GIS) and remote sensing. Landslide locations were identified from interpretation of satellite image and field surveys. The topographic, soil, forest, geologic, lineament and land cover data were collected, processed and constructed into a spatial database using GIS and remote sensing data. Using frequency ratio model which is one of the probability model, the relationships between landslides and related factors such as slope, aspect, curvature and type of topography, texture, material, drainage and effective thickness of soil, type, age, diameter and density of wood, lithology, distance from lineament and land cover were calculated as frequency ratios. Then, the frequency ratio were summed to calculate a landslide susceptibility indexes and the landslide susceptibility maps were generated using the indexes. The results of the analysis were verified and cross-validated using actual landslide location data. The verification results showed satisfactory agreement between the susceptibility map and the existing data on landslide locations.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1147-1150
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• 2008

The goal of this research is to apply the neural networks models for the disaggregation of the pan evaporation (PE) data, Republic of Korea. The neural networks models consist of the support vector machines neural networks model (SVM-NNM) and multilayer perceptron neural networks model (MLP-NNM), respectively. The SVM-NNM in time series modeling is relatively new and it is more problematic in comparison with classifications. In this study, The disaggregation means that the yearly PE data divides into the monthly PE data. And, for the performances of the neural networks models, they are composed of training, cross validation, and testing data, respectively. From this research, we evaluate the impact of the SVM-NNM and the MLP-NNM for the disaggregation of the nonlinear time series data. We should, furthermore, construct the credible data of the monthly PE data from the disaggregation of the yearly PE data, and can suggest the methodology for the irrigation and drainage networks system.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.4
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• pp.253-258
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• 2002

This paper reports the design, modeling, fabrication and measurement of passive microvalves, which are applicable to glaucoma implants. The proposed microvalves were designed using fluidic theory. The microvalves consisted of microchannels and chambers. The microchannels had a constant fluidic resistance generating a pressure difference. Six kinds of microvalves were designed using fluidic equations for laminar flow and fabricated to examine the influences of chamber size, channel length and the shape of channel cross section. The pressure difference between the designed microvalve and the fabricated microvalve was measured to be less than 4%.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.404-411
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• 2007

Reinforced roadbeds are valued from the point of view of maintenance as well as enhanced mechanical capacity. They support more train load and less transmit to the sub-layers than general roadbeds. Also, the lateral sloping surface of the reinforced roadbed and its low permeability, achieved by the controlled compaction, increase drainage capability and prevent the softening of sub-layers. In the study, a series of cross-hole tests was performed to observe the temporal changes in the stiffness of reinforced roadbeds, if any, due to the cyclic loading of trains and alternating rainy and frozen seasons at Pyeong-taek experimental site. The three types of reinforced roadbed materials are slag, crushed stones, and soils, and the thickness of all the reinforced roadbeds is 0.8m. The stiffness of the slag and soil reinforced roadbeds was not changed or slightly decreased. The stiffness of the crushed stone was somewhat increased and is inferred to being densified close to surface.

• Journal of Chest Surgery
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• v.25 no.12
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• pp.1455-1460
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• 1992

Anomalous drainage of the right superior vena cava into the left atrium is a very rare congenital cardiac anomaly. Recently a patient with this venous anomaly was surgically corrected and forms the basis of this report. Patient findings were as follows: The patient has no other symptom but cyanosis which prompted cardiac evaluation Chest PA and electrocariogram were usual. Cross-sectional echocardiogram showed normally connected heart without intracardiac defect, Inferior vena cava drained normally into right atrium and coronary sinus was not dilated. Contrast, given into the right atrium, appeared in the left atrium This rare venous anomaly was confirmed by surgery. Surgical correction consisted of division of superior vena cava above the junction of left atrium and reanastomosis into right atrial appendage. Postoperative digital subtracion angiography confirmed the successful repair. She has doing well for 6months since operation. Systemic venous anomalies without intracardiac defect are very rare. However this anomalies should be considered in the differential diagnosis of cyanosis. The successfully corrected case is reported and literature is reviewed.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1244-1248
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• 2007

This study aims at investigating the in situ applying grass concrete system in river environments which widely used nowadays and reviewing the effect and flow resistance for grass concrete structure through the physical experiments by hydraulic model test and developing application method in river bed which has rigid flood resistance. Grass concrete structure has been independently tested under high velocity flow under the super critical condition, as well as sud critical flow measuring velocity and water surface elevation along the cross section. This results shows grass concrete system is also suited to use in aggressive river environments such as repairing a flood damaged embankment that had placed at risk the adjacent drainage channel with vegetation.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.165-172
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• 2002

We presents an hazard zonation mapping technique in karst terrain and its assessment. From the detailed engineering geological mapping. Controlling factors of sink hole and limestone cave formation were discussed and 4 main hazard factors affecting hazard potential are identified as follows: prerequisite hazard factor(distributions of pre-existing sink holes and cavities), geomorphological hazard factors(slope gradient, vegetation, and drainage pattern etc.) geological hazard factors(lithology, fracture patterns and geological structures etc.) and hydraulic conditions(hydraulic head, annual fluctuation of ground water table and composition of g/w water). From the construction of hazard zonation map along the Jecheon-Maepo area, and vertical cross-sectional hazard zonations specific tunnel site we suggest hazard zonation rating systems.

• KCID journal
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• v.13 no.1
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• pp.39-49
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• 2006

Weather station based PET(Potential Evapotrarspiration) analysis has often been inadequate to meet the needs of regional-scale irrigation planning. A map of continuous PET surface would be better a solution for the spatial interpolation considering spatial variations. Using a normal PET data collected at the 54 meteorological stations in Korea, 10-days spatial distribution PET map was created using universal Kriging(UK). These estimation methods were evaluated by both visual assessments of the output maps and the quantitative comparison of error measures that were obtained from the cross validation. The universal Kriging method showed appropriate results in spatial interpolation from weather station based PET to spatial PET with low statistical errors.